The invention relates to a contact pin for testing microelectronic components having substantially spherical contacts, in particular ICs with BGA (Ball Grid Array) packs. The cylindrical free end of the contact pin interacts with the component contact to be tested.
Contact pins of this type are already commercially available.
IC modules are normally subjected to an electrical function test after their production. For this purpose, the connecting contacts or pads of the IC, which depending on the pack shape and connection technology may be designed very differently, are brought into contact with a number of contact pins that are electrically connected to an evaluation circuit or to a test device. The contact pins are in this case typically held in a cap or adapter, to be precise in a configuration that corresponds to the configuration of the connecting contacts.
For testing, the IC module is generally lowered with connecting contacts pointing downward onto the contact pins projecting from a cap. In order to ensure a sufficiently high contact force and hence a low contact resistance between the connecting contact and the contact pin, and in order to ensure that the contact pin and connecting contact are centered during the test, a mechanical pressure is in this case exerted on the rear face of the IC, from above. However, this is generally problematic, since it can lead to mechanical damage, in particular to a fracture of the IC module. The parts of the test configuration may be lowered and pressed into contact either by hand or in an automated manner.
The contact pins are commercially available in a large number of variations. In addition, spring contact pins, sometimes referred to as pogo pins, are also known, in the case of which at least one contact pin end can be moved axially with a defined spring force. Depending on the material, configuration and the sensitivity of the connecting contacts to be tested, the contact pin ends may, for example, be designed in the form of tips, crowns or in a rounded form at the contact end.
Special requirements for the testing technology arise in conjunction with testing IC modules with spherical or hemispherical (connecting) contacts arranged in a grid, in particular when testing modules of the BGA (Ball Grid Array) type. These also include, for example, so-called CSPs (Chip Size Packages). As a result of the necessary contact pressure, which is often not transmitted from the contact pin at right angles onto the lowermost point of the solder ball, but at an angle that is not desirable, the solder balls are frequently subject to the formation of grooves or to deformation. Overall, the known test arrangements for testing BGA contacts do not satisfy the requirements to which non-destructive testing is subject, especially after a number of contact cycles.
Published German Patent Application DE 195 33 272 A1 discloses a test contact that can be embedded in a cap and is not cylindrical at the contact end, but includes two resilient tongues which open in a V-shape and between which the contact ball is held such that it makes contact reliably, but is mechanically protected when the contact pressure is applied. The known test contact, which is intended to prevent the formation of grooves on the solder ball, is based on a force that is applied to produce the contact pressure, which as described above is generally not permissible. Furthermore, by virtue of its construction, the known test contact cannot be used universally.
U.S. Pat. No. 5,685,725 discloses a contact pin for testing microelectronic components having substantially spherical contacts, whose first end, which interacts with the component contact to be tested, is cylindrical.
Published Japanese Patent Abstract JP 200180469 A furthermore discloses a contact apparatus for testing microelectronic components having substantially spherical contacts, in which a mechanical and electrical contact is produced by the suction of an approaching component.
It is accordingly an object of the invention to provide a contact pin of the type mentioned initially which overcomes the above-mentioned disadvantages of the prior art apparatus of this general type.
In particular it is an object of the invention to provide a contact pin of the type mentioned initially, which allows reliable and non-destructive testing of components, in particular, of BGA components, with at most a minimal contact pressure.
With the foregoing and other objects in view there is provided, in accordance with the invention, a contact pin for testing a microelectronic component having a substantially spherical contact with a diameter. The contact pin includes a first contact pin end part having an end area. The contact pin end part is formed as a suction tube for providing a reduced pressure at the end area. The suction tube has an internal diameter that is less than the diameter of the spherical contact of the microelectronic component, so that a mechanical and electrical contact can be produced by sucking the spherical contact of the microelectronic component onto the end area of the first contact pin end part as the spherical contact of the microelectronic component approaches the end area of the first contact pin end part.
In accordance with an added feature of the invention, the contact pin includes a coaxial inner part; and an annular end area formed between the suction tube and the coaxial inner part. The suction tube forms a sleeve surrounding the coaxial inner part; and the reduced pressure is provided at the annular end area.
In accordance with an additional feature of the invention, the suction tube and the coaxial inner part have a cross-sectional area that widens toward the end area of the contact pin end part.
In accordance with another feature of the invention, the contact pin includes a suction collar configured on the end area of the first contact pin end part. The suction collar opens substantially in a hemispherical shape.
In accordance with a further feature of the invention, the suction collar is made of elastic material.
In accordance with a further added feature of the invention, the first contact pin end part is cylindrical.
In accordance with yet an added feature of the invention, the microelectronic component, with which the contact pin is used, includes a Ball Grid Array pack.
In accordance with yet another feature of the invention, the contact pin is a spring contact pin.
In the case of a contact pin of the type mentioned initially, the object of the invention is achieved by forming the free contact pin end as a suction tube in which a reduced pressure that acts on the end area of the free contact pin end can be produced. The diameter of the suction tube is less than the diameter of the component contact with which contact is to be made, so that a mechanical and electrical contact can be produced by sucking an approaching component contact onto the end area of the contact pin end.
The invention makes it possible to dispense with exerting pressure on the rear face of the component. An approach or slight contact between the contact pin end and component contact is sufficient in order to produce an electrical contact and a fixed-position configuration of the parts of the test system just by the suction force, and to maintain this without any disturbance of the electrical measurements being carried out. The mechanical load on the component and on its spherical contacts is considerably less than in test systems using the known contact pins.
In one preferred embodiment, the suction tube surrounds a coaxial inner part like a sleeve, and the reduced pressure can be produced in an annular end area between the suction tube and the inner part. This results in an annular suction zone, which leads to robust positioning and force action on the solder balls.
These effects can be further reinforced by widening the cross section of the configuration including the suction tube and the coaxial inner part, toward the end area of the contact pin end.
The suction effect and the positioning can also be reinforced by arranging a suction collar, which opens substantially in a hemispherical shape and into which the solder balls are inserted during suction, on the end area of the free contact pin end.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a contact pin for testing microelectronic components having substantially spherical contacts, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.